الفهرس 
Spectrophotometric Methods for Simultaneous Determination of Velpatasvir and Sofosbuvir in their Dosage FormOnly 14 pages are availabe for public view
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Abstract
This thesis presents new chromatographic and spectrophotometric methods for determination of selected drugs in bulk form and in their pharmaceutical dosage forms. The drugs selected for this study are: Velpatasvir (VEL) in combination with Sofosbuvir (SOF), Daclatasvir (DAC) and Ledipasvir (LPV) in combination with Sofosbuvir (SOF). The thesis consists of four parts: Part I This part describes a general introduction about hepatitis C virus life cycle and different classes of Direct Acting Antivirals (DAAs) and their mechanism of action. Part II This part is divided into three sections: Section A: Spectrophotometric methods for determination of velpatasvir and sofosbuvir in their dosage form. This section included two methods; first derivative of ratio spectra for the simultaneous determination of VEL and SOF in binary mixture without any interference. The peak amplitudes were measured at 287.4 nm for VEL and 245.8 nm for SOF, respectively. Linear relationships were obtained between the peak amplitude at 287.4 nm and the corresponding concentrations 5.0-45.0 μg/mL for VEL and at 245.8 nm against the corresponding concentration 5.0-50.0μg/mL for SOF. The proposed method was successfully applied for the determination of VEL and SOF in their dosage form with mean percentage recovery 99.73±0.445 and 99.58±0.570 for VEL and SOF, respectively. The second method is a ratio difference spectrophotometric method (RD) in which the ratio spectra of different VEL standards at increasing concentration in methanol was obtained by dividing each by the spectrum of 10.0 μg/mL SOF in the same solvent then the amplitudes of peak to trough between 231.4 and 253.4 nm on the generated ratio spectra were directly proportional to VEL concentration and for the determination of SOF, the same procedure was followed, the ratio spectra of different standards of SOF using10.0 μg/mL VEL as divisor. The peak to trough amplitude between 245.8 and 238.4 nm were measured and found proportional to SOF concentration. The linearity ranges were 5.0- 45.0 μg/mL and 5.0-50.0 μg/ mL for VEL and SOF, respectively. The method was successfully applied for the determination of VEL and SOF in their pharmaceutical dosage form with mean % recovery ±SD 7..001 ± 0.197 and 99.73 ± 1.032 for VEL and SOF, respectively. Section B: UPLC method for the simultaneous determination of velpatasvir and sofosbuvir in their dosage form. This section included simultaneous determination of VEL and SOF in their dosage form by UPLC using mobile phase consisting of a mixture of 0.05 M diammonium phosphate buffer pH 6±0.2: acetonitrile (40:60, v/v) on a reversed phase C18 column, at flow rate 0.1 mL/min and detection wavelength at 280 nm. Good linearity was obtained in the ranges from 10.0-90.0 μg/mL and 10.0-240.0 μg/mL for VEL and SOF, respectively, with mean percentage recoveries 100.75±0.559 and 99.95±0.717 for VEL and SOF, respectively. Robustness evaluation was performed by means of Youden’s test which examines, within one single laboratory, the susceptibility of analytical methods against small changes in the method parameters using experimental designs. Section C : TLC-Densitometric Method for Simultaneous Determination of Velpatasvir and Sofosbuvir in their dosage form. This section included the determination of VEL and SOF using RP TLC, the developing system was consisting of chloroform- methanol- ammonia (90: 9: 1 by volume) and UV detection at 280 nm for VEL and SOF. Good linearity were obtained in the concentration ranges of 0.05-0.5μg/μL for VEL and 0.2-1.0 μg/μL for SOF with mean percentage recovery 100.52±0.661 and 100.46±0.511, for VEL and SOF, respectively in their pharmaceutical dosage form using standard addition technique. Part III: This part consists of two sections Section A: Stability indicating Ultra-performance Liquid chromatographic Method for Determination of Daclatasvir. This section included the determination of the drug in presence of its degradation products using UPLC. DAC was refluxed with 5 M hydrochloric acid and 5 M sodium hydroxide for 8 h, two degradates for each reagent was produced and identified using LCMS. The mobile phase consists of a mixture of 0.02 M ammonium phosphate buffer pH 3±0.2: methanol (40:60, v/v). The separation was performed on C18 column at a flow rate of 0.4 mL/min and UV detection at 305 nm. The calibration concentration range was 100.0–700.0 μg/mL. The mean % recovery ±SD was 99.78 ±0.632 in the pharmaceutical dosage form. The degradation products were identified by LC-MS. Section B: Stability indicating HPLC method for determination of Daclatasvir using Fluoresence detection. The separation was performed using phenyl column, the mobile phase consists of a mixture 0.02 M ammonium phosphate buffer pH 3±0.2: methanol (40:60, v/v), the flow rate was 1mL/min, the detection was performed at λex305nm and λem 457nm for excitation and emission, respectively. Linear relationship was obtained between the peak area and the concentration of the drug in the range of 0.05-2.00 μg/mL, with mean percentage recovery 101.12±0.655. Part IV: UPLC method for the simultaneous determination of Ledipasvir and Sofosbuvir in their dosage form. UPLC method was applied for simultaneous determination of LPV and SOF using C18 column, the mobile phase consists of a mixture of 0.1% ammonium acetate buffer pH 6±0.2: acetonitrile (40:60, v/v) and UV detection at 245 nm. Good linearity were obtained with ranges from 10.0 to 90.0 μg/mL and from 20.0 to 280.0 μg/mL for LPV and SOF , respectively with mean % recoveries ±SD were 99.80 ± 1.407 and 100.59 ±0.823 for LPV and SOF, respectively. The thesis consists of 41 Figures, 38 Tables and 99 References and ends in an Arabic summary.